Cambium

Cambium, from a Latin word meaning to change, is a name which was originally applied to all those tissues in plants which, retaining the protoplasm in their cells and their originally thin walls, are capable of undergoing cell-division and thus growing. These are now collectively called meristem (q.v.), the term cambium being restricted to that ring of meristem that occurs between the wood (xylem) and bast (phloem) of exogenous stems, i.e. those of gymnosperms and dicotyledons. This ring is partly fascicular, or formed within the fibro-vascular bundles, partly interfascicular; and its elements, which are often elongated, form either wood-cells on its inner surface or phloem-cells externally. The name pericambium is applied to the merismatic inner layer of the cortex of roots; procambium, to the elongated narrow cells that foreshadow the whole fibro-vascular bundle; and cork-cambium, to the phellogen or merismatic layer of cortex which forms secondary cortex or periderm.